1. Field of the Invention
This invention relates to a three-dimensional model processing method and apparatus for forming a three-dimensional model of an object, editing the model, adding shading or the like and displaying the model, without relying upon the data format of inputted three-dimensional data.
2. Description of the Related Art
Various three-dimensional model processing apparatus have been disclosed heretofore. In one example of such an apparatus, three-dimensional position data indicative of the surface of an actual object such as a clay model are entered by a contacting-type three-dimensional coordinate measuring unit such as a three-dimensional digitizer, and a three-dimensional model is created from the entered three-dimensional data. In another example, the aforementioned three-dimensional position data are entered by a space-sectioning type three-dimensional measuring unit and a three-dimensional model is created from these three-dimensional data.
A three-dimensional model processing apparatus of this kind makes it possible to create a three-dimensional model from three-dimensional data.
In accordance with the conventional three-dimensional model processing apparatus, however, the three-dimensional data are entered in a data format that is dependent upon the three-dimensional measuring unit, and therefore a three-dimensional model cannot be created by processing three-dimensional data having a different data format. In addition, once a three-dimensional model has been created, the three-dimensional data cannot be converted into three-dimensional data having another format.
Several specific examples will now be described.
A range-image processing method, in which a range image is the object of processing and information indicating the characteristics of the surface shape of a three-dimensional object in the image is detected, is described in "A Hybrid Approach to Range Image Segmentation Based on Differential Geometry" by Naokazu Yokoya and Martin D. Levine, Joho Shori Gakkai Ronbunshi, Vol. 30, No. 8, pp. 944.about.953 (1989).
In this conventional technique for processing range images, however, the relationship between the coordinate system in which an object is placed and the coordinate system of the image is not defined, and it is necessary to give parameters such as the aspect ratio along each of the coordinate axes each time processing is performed.
Various types of non-contacting arrangements have been attempted. For example, there is a method of measuring the time of flight of light or a method in which distance data are inputted by a three-dimensional measuring unit such as a range finder based upon triangulation, and a three-dimensional model is created from the three-dimensional data obtained.
In a three-dimensional model creating apparatus which utilizes such a three-dimensional measuring unit, an input sensor is directed with respect to the object to be entered, and points not concealed by other objects can be inputted accurately. However, a drawback is that distance data regarding portions in back of the input sensor and points that are concealed cannot be inputted.
In an effort to eliminate this drawback, a three-dimensional model is obtained by either of the following methods in the prior art: (1) The sensor is fixed and the object is revolved about a main axis, in synchronization with which a range image is measured. (2) The sensor is revolved about the object, in synchronization with which a range image is measured.
However, both of these methods require a mechanism for revolving the object or the sensor. In addition, it is not easy to reconstruct a three-dimensional shape by judging corresponding pixels of a plurality of range images.
In general, when an image in which an object in three-dimensional space is projected into two-dimensional space is outputted, shading is applied. Then, when the image is displayed, for example, images in which the object is seen from a plurality of directions are displayed in continuous fashion, whereby the orientation of the object surface is outputted so that the object in three-dimensional space is expressed in two-dimensional space.
With this conventional method, however, the entirety of the surface shape of the object in a certain three-dimensional space cannot always be outputted in the form of a single two-dimensional image.
In another example of a conventional three-dimensional model processing apparatus, it has been attempted to input three-dimensional coordinate data indicative of the surface of an object by a three-dimensional coordinate measuring unit such as a laser range finder, and create a three-dimensional model by triangular patches in which all of the three-dimensional coordinate data serve as the vertices. Alternatively, it has been attempted to create a three-dimensional model based upon triangular patches in which some of the original data are adopted as the vertices, as by widening the spacing between neighboring points of the three-dimensional coordinates serving as the vertices. A three-dimensional model is capable of being created from three-dimensional data in a three-dimensional model processing apparatus of this kind.
Further, in another example of a conventional three-dimensional model processing apparatus, it has been attempted to input three-dimensional data, which are indicative of the surface of an actual object such as a clay model, by a contacting-type three-dimensional measuring unit such as a three-dimensional digitizer, and create a three-dimensional model from these three-dimensional data. Further, it has been attempted to enter the three-dimensional position data by a space-sectioning type three-dimensional measuring unit and create a three-dimensional model from these three-dimensional data.
In addition, attempts have been to utilize the obtained three-dimensional objects in various animation or CAD/CAM techniques.
With the conventional three-dimensional model processing apparatus, however, the three-dimensional model is created by selecting representative points uniformly over the entire area of the object surface from the three-dimensional coordinate data of the object surface inputted by the three-dimensional coordinate measuring unit such as the aforementioned laser range finder, and creating the model based upon polygonal patches in which the uniform representative points serve as the vertices. A problem which arises is that the amount of data representing the model becomes extremely large when it is attempted to raise accuracy.
The amount of data can be reduced somewhat in the case of the three-dimensional model created by the triangular patches in which some of the data serve as the vertices, wherein the spacing between neighboring points of the three-dimensional coordinates serving as the vertices is widened. However, at complicated portions or curved surfaces where the shape is highly irregular, the surface of the object cannot be described correctly. On the other hand, the vertices of polygonal patches are placed at intervals equal to those of other portions even in large planar areas, and therefore unneeded data also is present.
Further, if it is desired to create 3-D animation video, in the prior art, this is possible only when a specialist or a CG animator utilizes an expensive system. An amateur encounters great difficulty when describing the modeling and moving of 3-D shapes. These systems can be utilized effectively only by relying upon manual operations or the artistic expertise of craftsmen, and many operations, such as modeling and the designation of motion, cannot be performed automatically.